Swinging bucket rotor assembly

ABSTRACT

A swinging bucket centrifuge rotor having a plurality of machined bucket receiving cavities with a hanger disposed in each cavity. The cavity includes surfaces which guide a bucket cap hook to facilitate engagement of the hanger by the hook to support the bucket in the cavity and further guide the bucket as it swings.

United States Patent [1 1 Chulay SWINGING BUCKET ROTOR ASSEMBLYlnventor: Steven J.'Chu1ay, Los Altos, Calif.

Assignee: Beckman Imtruments, Inc., Fulletwn allf,

Filed: Apr, 4, 1972 Appl. No.: 240,968

Int. Cl. B041) 9/12 Field of Search 233/26, 1 R, 27, 233/28 ReferencesCited UNITED STATES PATENTS 7/1968 Galasso et al 233/26 4/1962 Blurn233/26 US. Cl. 233/26 Aug. 14, 1973 3,377,021 4/1968 Fox et al 233/26FOREIGN PATENTS OR APPLICATIONS 925,817 3/1955 Germany ..L 233/26894,010 10/1953 Germany 233/26 Primary Examiner-George H. KrizmanichAttorneylfaulD Flehr, Aldo J. Test et al.

[57] ABSTRACT 9 Claims, 6 Drawing Figures Patented Aug. 14, 1973 2Shets-Sheet 2 1 SWINGING BUCKETROTOR ASSEMBLY BACKGROUND OF THEINVENTION This invention relates generally to high speed swinging bucketcentrifuge rotor assemblies and more particularly to a centrifuge rotorassembly including a hanger disposed in a rotor head cavity which isformed to receive and guide a bucket cap hook onto the hanger forsecurely supporting and guiding the associated bucket.

Swinging bucket centrifuge rotor assemblies have included rotor headswith cavities each provided with cross pins which are inserted in thehead to engage a bucket support and removed to disengage the bucket fromthe head. The bucket includes ears with holes through which the crosspin passes to swingingly support the bucket. A difficulty with suchprior art rotors is that because of the rotor head geometry required toaccommodate a cross pin, the number of cavities is limited. To overcomethe latter restriction, hangers have been constructed to dispose a crosspin or cross pin support in the cavity. The bucket or its cap isprovided with hooks which are spaced apart a distance greater than thetube carried by the bucket. This designis subject to either improperhooking or to dislodging during movement of the rotor. Another type ofrotor employs a cross pin at the end of an elongated hanger. However,this rotor requires complex machining to assure proper functioning ofthe hanger and hook.

OBJECTS AND SUMMARY OF THETNVENTION It is a general object of thepresent invention to provide an improved swinging bucket centrifugerotor assembly.

It is another object of the invention to provide a swinging bucketcentrifuge rotor assembly including a rotor having a plurality ofcavities each provided with a hanger adapted to receive an improvedbucket cap.

'It is a further object of the present invention to provide a centrifugerotor assembly in which a hanger supports the bucket and serves as aspring as the bucket swings from the vertical to the horizontal positionduringcentrifuge operation and guides the bucket cap as the bucketswings to the horizontal position.

It is another object of the present invention to provide an improvedbucket cap which can be manually threaded onto the bucket without theuse of a tool.

It, is a further object of the present invention to provide a rotorassembly in which the part of the cavity for receiving the hanger withcross pin and a bucket cap is formed in three simple machiningoperations. One part serves to guide the bucket cap towards a slot whichguides the cap onto the cross pin where it is securely held on the crosspin. The slot also provides a guide for thebucket as it swings about thecross pin during a centrifuge operation.

The foregoing and other objects are achieved by a centrifuge rotorincluding a plurality of bucket receiving cavities with means in saidcavities for supporting the bucket in a vertical position and allowingthe bucket to swing into a horizontal position during centrifugation.Each of said cavities includes a pocket provided with a cross pin andhaving a slotted wall with the slot adapted to receive a relatively flatbudket cap to guide the same onto the pin and guide the bucket capduring swinging movement of the bucket from the vertical to thehorizontal position.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of arotor in accordance with the present invention.

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is an enlarged view taken along the lines 3-3 of FIG. 1.

FIG. 4 is an enlarged view showing the deflection of the cross pinholder during centrifuge operation.

FIG. Sis a view taken along the line 5-5 of FIG. 3.

FIG. 6 is a sectional view of the centrifuge rotor assembly showing thecavity and supported swinging bucket. r

DESCRIPTION OF PREFERRED EMBODIMENT The rotor comprises a body 11 whichis provided with a plurality of cavities 12 which accommodate swingingbuckets 13. FIG. 1 shows the rotor in its stationary condition with thebuckets 13 depending vertically downward. FIG. 6 shows the rotorassembly under centrifugation with the swinging bucket 13 in thehorizontal position. The bucket shoulder 14 is seated against the rotorseat 16 to limit outward movement of the bucket during centrifugation.

In accordance with the present invention, there is provided an improvedhanger assembly for the swinging buckets. The assembly includes a hanger17, FIGS. 2, 3, 4 and 5, having an. elongated body 18 with a cross pin19 secured at the lower end. The hanger body 18 is disposed in hole 20extending through the rotor parallel to and spaced from the axis of therotor. As will be presently described, the cross pin is engaged by thebucket cap hooks to support the bucket. The body 18 also serves as aspring which deflects, as indicated in FIG. 4, when centrifugal forcesact on the bucket whereby the bucket seats against the rotor seat. Thecross pin 19 has its ends 21, FIG. 2, machined with a radius Rcorresponding to the radius R of surface 22 of the wall of pocket 23whereby during centrifugation and deflection of the body 18, the ends ofthe cross pin are seated on the surfaces 22. When a bucket is beingcarried, the cross pin is not seated until after the bucket shoulder 14contacts the rotor seat 16. Under extremely high forces, the boss 24formed on the body 18 will seat against the wall of hole 20. This limitsdeflection of the body 18. The hanger is positioned axially in the hole20 by means of a screw 26 which screws into the threaded hole 27 at thetop of the hanger body 18. The hanger body is split at 28 whereby whenthe screw is threaded into the hole, it expands the upper end of thebody and locks the hanger in the rotor.

In accordance with another feature of the invention, there is providedan improved bucket cap 30 which has a flat stern portion with the upperhooked end slotted 31 to form a pair of spaced hooks or tangs 32 whichserve to straddle the body 18. It is impossible to attach the bucketassembly to the cross pin with only one of two hooks engaged. Thecooperation between the slot 31 and body 18 serves to guide the bucketas it swings from the horizontal to the vertical position.

As described, cavities 12 each include a pocket 23 formed by a simplemachine operation and which is concentric to the hanger stern and hole20. Cavity 12 also includes an adjacent cut or well 37 which serves as aguide to guide hooks or tangs 32 of the bucket cap as the bucket isinserted in the rotor cavity. The wall separating the pocket 23 and well37 is slotted to form slot 38. The slot width is slightly wider than thewidth across the outside tangs 32 whereby it guides the hook inwardly toassure that the spaced tangs straddle the hanger body 18. The slotcooperates with the hanger body 18 to guide the bucket as it swings.Preferably, the depth of the pocket 23 is controlled to provide aminimum clearance above the cross pin to minimize the possibility ofunhooking when the rotor is moved about.

Thus, there has been provided an improved swinging bucket centrifugeassembly in which the rotor cavities and bucket caps cooperate to guidethe bucket cap to easily engage the hanger pin and which guide the rotorcap as the bucket swings. The bucket cap is shaped to provide a firmgrip to unscrew the cap from the associated bucket without the need fora tool. The entire rotor assembly occupies a minimum space makingavailable more load carrying capacity.

I claim:

1. A centrifuge rotor of the type including a rotor head having aplurality of cavities configured for receiving buckets having enlargedshoulders and means in each of said cavities for supporting a bucket bya bucket cap having hook means, the bucket being supported in a verticalposition and being allowed to swing into a horizontal position where theshoulder seats on a portion of said cavity during centrifugation theimprovement comprising for each cavity a pocket formed within saidcavity for receiving at least a portion of said hook means, a hole forretaining the bucket supporting means, said hole extending through therotor spaced from and parallel to the axis of the rotor communicatingwith said pocket, a well formed within said cavity and spaced radiallyoutwardly from the pocket forming a portion of said rotor therebetween,and a slot in that portion of the rotor, said slot having a widthsufficient for passage therethrough of the hook means of the bucket cap.

2. A centrifuge rotor assembly of the type including a rotor body havinga plurality of bucket receiving cavities and pin means in said cavitiesadapted to support an associated bucket in a vertical position andallowing it to swing into a horizontal position where it moves outwardlyto seat on a portion of said cavity during a centrifugation operationthe improvement comprising for each cavity a pocket formed within saidcavity, a hole extending through the rotor spaced from and parallel tothe axis of the rotor communicating with said pocket, a well formedwithin said cavity and spaced radially outwardly of the rotor axis, saidrotor being slotted for forming a guide slot extending between saidpocket and well, said pin means including an elongated hanger extendingthrough said hole with one end disposed in said pocket and a cross pinsecured to said one end of the hanger, said cross pin including endportions shaped for seating on the adjacent wall portions of said pocketunder the action of centrifugal force.

3. A rotor assembly as in claim 2 wherein the upper portion of saidhanger includes a split threaded hole, a screw in said threaded hole forsecuring the hanger to the rotor body.

4. A rotor assembly as in claim 3 wherein said hanger includes a bossengaging the wall of said hole when the hanger is deflected apredetermined amount.

5. A centrifuge rotor assemblyof the type including a rotor body havinga plurality of cavities configured for receiving buckets having enlargedshouders and pin means in said cavities adapted to support an associatedbucket in a vertical position and allowing it to swing into a horizontalposition where the shoulder seats on a portion of said cavity duringcentrifugation the improvement comprising for each cavity a generallycylindrical pocket formed within said cavity, a hole extending throughthe rotor spaced from and parallel to the axis of the rotorcommunicating generally centrally with said pocket, a well formed withinsaid cavity and spaced radially outwardly from said pocket forming aportion of said rotor therebetween, a guide slot cut into said portion,said pin means being secured within said hole and extending into saidpocket, and a bucket cap including at least one hook engaging said pinmeans to support the bucket, said hook including a flat stem portionadapted to cooperate with said guide slot to guide the stem portion.

6. A rotor assembly as in claim 5 wherein said pin means include across-pin at the end of a hanger disposed in said hole and said hook isslotted to form spaced portions straddling said hanger.

7. A rotor assembly as in claim 5 wherein said hanger includes a bossengaging the wall of said hole when the hanger is deflected apredetermined amount.

8. A rotor assembly as in claim 4 wherein said hole has a substantiallyuniform cross section and said hanger is tapered downwardly with theupper portion thereof having approximately the same cross-section assaid hole, said boss being disposed adjacent the lower edge of saidhole.

9. A rotor assembly as in claim 7 wherein said pin is a cross pinsecured to the free end of said hanger, said cross pin including endportions shaped for seating on the adjacent wall portions of saidpocket, the parts of said rotor assembly being so configured that underthe action of the centrifugal force after the shoulder of the bucket isseated on a portion of said cavity said cross pin travels an additionaldistance to seat on said wall portion to relieve the strain of the hookon said cross pin.

i i t t

1. A centrifuge rotor of the type including a rotor head having aplurality of cavities configured for receiving buckets having enlargedshoulders and means in each of said cavities for supporting a bucket bya bucket cap having hook means, the bucket being supported in a verticalposition and being allowed to swing into a horizontal position where theshoulder seats on a portion of said cavity during centrifugation theimprovement comprising for each cavity a pocket formed within saidcavity for receiving at least a portion of said hook means, a hole forretaining the bucket supporting means, said hole extending through therotor spaced from and parallel to the axis of the rotor communicatingwith said pocket, a well formed within said cavity and spaced radiallyoutwardly from the pocket forming a portion of said rotor therebetween,and a slot in that portion of the rotor, said slot having a widthsufficient for passage therethrough of the hook means of the bucket cap.2. A centrifuge rotor assembly of the type including a rotor body havinga plurality of bucket receiving cavities and pin means in said cavitiesadapted to support an associated bucket in a vertical position andallowing it to swing into a horizontal position where it moves outwardlyto seat on a portion of said cavity during a centrifugation operationthe improvement comprising for each cavity a pocket formed within saidcavity, a hole extending through the rotor spaced from and parallel tothe axis of the rotor communicating with said pocket, a well formedwithin said cavity and spaced radially outwardly of the rotor axis, saidrotor being slotted for forming a guide slot extending between saidpocket and well, said pin means including an elongated hanger extendingthrough said hole with one end disposed in said pocket and a cross pinsecured to said one end of the hanger, said cross pin including endportions shaped for seating on the adjacent wall portions of said pocketunder the action of centrifugal force.
 3. A rotor assembly as in claim 2wherein the upper portion of said hanger includes a split threaded hole,a screw in said threaded hole for securing the hanger to the rotor body.4. A rotor assembly as in claim 3 wherein said hanger includes a bossengaging the wall of said hole when the hanger is deflected apredetermined amount.
 5. A centrifuge rotor assembly of the typeincluding a rotor body having a plurality of cavities configured forreceiving buckets having enlarged shouders and pin means in saidcavities adapted to support an associated bucket in a vertical positionand allowing it to swing into a horizontal position where the shoulderseats on a portion of said cavity during centrifugation the improvementcomprising for each cavity a generally cylindrical pocket formed withinsaid cavity, a hole extending through the rotor spaced from and parallelto the axis of the rotor communicating generally centrally with saidpocket, a well formed within said cavity and spaced radially outwardlyfrom said pocket forming a portion of said rotor therebetween, a guideslot cut into said portion, said pin means being secured within saidhole and extending into said pocket, and a bucket cap including at leastone hook engaging said pin means to support the bucket, said hookincluding a flat stem portion adapted to cooperate with said guide slotto guide the stem portion.
 6. A rotor assembly as in claim 5 whereinsaid pin means include a cross-pin at the end of a hanger disposed insaid hole and said hook is slotted to form spaced portions straddlingsaid hanger.
 7. A rotor assembly as in claim 5 wherein said hangerincludes a boss engaging the wall of said hole when the hanger isdeflected a predetermined amount.
 8. A rotor assembly as in claim 4wherein said hole has a substantially uniform cross section and saidhanger is tapered downwardly with the upper portion thereof havingapproximately the same cross-section as said hole, said boss beingdisposed adjacent the lower edge of said hole.
 9. A rotor assembly as inclaim 7 wherein said pin is a cross pin secured to the free end of saidhanger, said cross pin including end portions shaped for seating on theadjacent wall portions of said pocket, the parts of said rotor assemblybeing so configured that under the action of the centrifugal force afterthe shoulder of the bucket is seated on a portion of said cavity saidcross pin travels an additional distance to seat on said wall portion torelieve the strain of the hook on said cross pin.